Historical data proves link between Big Chino aquifer, Upper Verde River
In both a written and then an oral presentation of the Montgomery and Associates review of a recently published U.S. Geological Survey (USGS) report to the Upper Verde River Watershed Protection Coalition June 27, the firm's representative, Ed McGavock, was critical of a Geologic Framework of Aquifer Units and Ground-Water Flowpaths, Verde River Headwaters, North-Central Arizona (by Wirt and others, 2005).
McGavock was particularly critical of a referenced report sources of springs supplying base flow to the Verde River headwaters, Yavapai County, Arizona: U.S. Geological Survey Open-File Report 99-0378 by Wirt and Hjalmarson, 2000).
Wirt and Hjalmarson concluded that the lowest mean daily flow of record at the USGS streamflow gage near Paulden gage of 15 cfs during May 13-23, 1964, coincided with pumping to fill artificial lakes constructed for real estate promotion near Wineglass Ranch in Big Chino Valley. Wirt and Hjalmarson also suggested there was a hydraulic connection between the Big Chino aquifer and the Verde River base flow.
In his presentation, McGavock not only said this story never happened based on his incorrect understanding of artificial-lake pumping and changes in base flow in the Verde River, but he also incorrectly assumed what I was thinking while collecting and reviewing hydrologic data during the 1960s as an employee of the USGS.
In particular, McGavock was not correct when he said that I had made no connection between the short-term 25 percent decrease in base flow and lake-supply pumpage at this time because I knew there was none.
I'd like to discuss this story that "never happened." As a young engineer in the early 1960s, I worked in the Upper Verde River area. Among other tasks, I assisted in selecting the site for the Verde-Paulden gage (that was installed in 1963), collected groundwater data such as water levels at index wells (wells that water levels were measured in by the USGS on a long-term basis) and groundwater pumping for farming. I also collected and reviewed surface-water data.
While documenting groundwater information I had collected during 1964-65, I included information about the artificial-lake filling at the Holiday Lake subdivision located at the lower end of Big Chino Valley next to Highway 89. I also summarized information concerning past lake filling that I learned while inspecting the area with the owner of the Holiday Lakes subdivision whom reported that the artificial lakes had also been filled during 1960, 1961 and 1962. This first period (1960-65) corresponds to the lowest water levels recorded in a nearby USGS index well, the same index well used in the USGS report Hydrogeology of the Upper and Middle Verde River Watersheds, Central Arizona, by Blasch and others (2006), for the lower end of Big Chino Valley.
During this period (1960-65) base flow at the Verde-Paulden gage also dropped from about 20 cfs to 15 cfs, the lowest base flow recorded at the site to this time. Lake-filling pumping at Holiday Lakes also occurred in 1970-72 and the base flow at the Verde-Paulden gage dropped to 16 cfs during this same time period. The significance of these low discharges and low groundwater levels was not recognized at the time because of the short operational history of the gage.
Clearly McGavock's conclusion that the lowest mean daily flow of record at the USGS streamflow gage near Paulden gage of 15 cfs during May 13-23, 1964, and 16 cfs during March 15, 1972, did not coincide with pumping to fill artificial lakes constructed for real estate promotion near Wineglass Ranch in Big Chino Valley is incorrect. His inappropriate and incorrect assumption that I was aware that there was no connection between the two as a young engineer collecting this data during the 1960s is also wrong.
Whether there is a one to one relationship between the pumpage and the two lowest recorded periods of baseflow cannot be fully established at this time, but in his criticism of me, McGavock offers no alternative reason for these two periods.
Certainly, it is now fully recognized that ground-water in the Big Chino Valley discharges to the upper Verde River and that withdrawal of this water by wells reduces the amount of ground-water discharging to the river by an amount equal to or nearly equal to the withdrawal. Wirt and Hjalmarson also suggested there was a hydraulic connection between the Big Chino aquifer and the Verde River base flow.
This fact is now widely recognized.
Win Hjalmarson of Camp Verde is the co-author of the Verde River headwaters, Yavapai County, Arizona: U.S. Geological Survey Open-File Report 99-0378 by Wirt and Hjalmarson, 2000).